Known aircraft structures comprise a fuselage and lifting surfaces located at both sides of the fuselage such as wings or pylons for supporting the engines of the aircraft or other supporting structures.
Known fuselages comprise a plurality of frames, stringers and beams, which act as reinforcing members of the aircraft skin. In order to integrate lifting surfaces with fuselage structures, an opening is usually performed in the fuselage skin, often implying an interruption in the structure of some of the frames of said fuselage.
Lifting surfaces may be divided into two or three independent parts, a central box located inside the fuselage and two lateral boxes located at both sides of the fuselage or, as an alternative, the lifting surfaces can be divided into two lateral boxes joined at the symmetry axis of the aircraft. Structural boxes comprise at least a front spar and a rear spar extending in the longitudinal direction of the torsion box, upper and lower skins and ribs extending in the transversal direction of the structural box.
Wings are usually located at upper or lower positions with respect to a fuselage section while pylons are usually located at a central position of a fuselage section.
Regarding pylons, a first known configuration may include a pylon extending between both engines and located at a centered position of the height of the cylindrical part of the fuselage. The central part of the pylon is introduced into the fuselage, therefore said configuration implies a discontinuity or, at least, a cut-out in the fuselage skin, with the associated impact in the loads distribution. In some cases, it even entails the discontinuity of some other structural elements such as stringers, longitudinal beams or frames.
The interface between lateral boxes of the lifting surfaces and the fuselage is usually solved by tension bolts and/or shear rivets. The junction joins the two lateral boxes to the rear part of the fuselage and a significant number of tension bolts need to be installed. Furthermore, the fuselage cylindrical skin needs to be adapted to the flat surface of the junction making the manufacturing and assembly process very complex.